This invention relates to an optical system for imprinting information such as characters, numerals or marks on the photographed image of a color television camera.
Imprinting dates or characters on photographed pictures, motion picture films and television pictures is very convenient because the dates or characters can be utilized as records in putting these pictures in order.
In general, in a character imprinting device in a camera, the image of characters is projected onto the image forming surface from behind it or from the lens housing, in order to imprint the characters. However, in a camera such as television camera using an image pick-up tube or a solid image pick-up element, it is impossible to imprint characters from behind the image forming surface because of its structure.
A system in which a character imprinting device is incorporated in a lens housing is known in the art. However, this system is undesirable for a camera having interchangeable lenses for the following reasons. In such a camera, the character imprinting device must be incorporated in each of the interchangeable lenses. Furthermore, it is necessary to provide a battery on the lens side as a power source for a lamp, lighting characters to be imprinted or for light emitting diodes forming characters. Alternatively, it is necessary to an provide electrical contact at the junction between the camera body and the lens to receive electric supply from the camera body. Accordingly, the camera becomes intricate in construction and bulky in size. Furthermore, the weight and cost are necessarily increased.
The image of characters may be formed in a photographed image by providing an optical component such as a half mirror, a mirror or a prism in a photographing optical system shown in FIG. 1. However, in this case, the peripheral portions around the characters are darkened. This results in a product that is undoubtedly poor in appearance. Furthermore, in the case where imprinting characters is not carried out, that portion is shadowed dark, and the photographed image is partly vignetted. Thus, the quality of the image is poor.
This difficulty can be overcome by moving the optical component such as a mirror or a prism outside the photographing optical system when the imprinting of characters is not carried out. However, to do so, it is necessary to provide a mechanically moving component or additional components. As a result, the manufacturing cost is increased, and the camera becomes intricate in construction and bulky in size. This in turn leads to an increase in the probability of difficultly in operation and reliability. Thus, the method is undesirable.
In composing characters or the like in a television image, two cameras are used. One of the cameras photographs an object to form the television picture, while the other camera takes a picture of a chart on which characters or the like are provided. These two images are subjected to composition, or the characters or the like are imprinted electrically. However, it is difficult for an ordinary amateur to do so because the equipment is expensive and the level of technique required for operating the equipment is very high.